In humans and other animals, exercise, strenuous training, and exposure to elements (e.g., sunlight, wind, rain, cold and heat) can result in significant physiological changes. Subjects exercising or training are at risk for developing injuries (e.g., muscle and/or tendon damage), especially subjects doing so in extreme conditions (e.g., cold or heat, high altitude, long durations, high intensity, repetitive, aerobic, contact sports, etc.). For example, excessive heat temperatures, in particular, environmental heat illnesses include but are not limited to heat syncope, heat exhaustion, dehydration syndrome, and heat stroke. The potentially fatal clinical syndrome of heat stroke has been described in marathon runners, military recruits, football players, and in hot industrial environments. An epidemic appearance of heat stroke has been described during heat waves in urban areas (Ferguson, M., And M. M. O'brien, “Heat Stroke In New York City: Experience With 25 Cases,” N.Y. State J. Med. 60:2531-2538, 1960).
Likewise, impaired or incomplete recovery following high-intensity exercise can negatively affect physical performance and delay functional progression, thereby reducing an athlete's chance of performing at his or her peak level. Athletes are constantly seeking ways to prevent exercise-induced muscle damage and facilitate muscle recovery from strenuous exercise. For example, athletes have used dietary supplements extensively to facilitate tissue growth and repair following muscle-damaging events such as high-intensity resistance exercise and participation in contact sports. Following strenuous exercise, an acute inflammatory response drives the repair process by synthesizing and releasing chemical mediators locally in the injured muscle. However, while inflammatory mediators may help attract growth factors used for protein synthesis and muscle repair, excessive inflammatory response may damage muscle and thereby hinder the repair process.
“Dehydration syndrome” may be characterized and/or accompanied by loss of appetite and limited capacity for work. Evidence of heat exhaustion becomes apparent with losses of, for example, 5% of the body water, and at about 7% loss of body water disorientation and hallucinations may occur. Losses of body water of 10% or greater are extremely hazardous and lead to heat stroke and death if not treated immediately. Heat stroke is accompanied by high body temperature (41.1° C.-43.3° C.; 106° F.-110° F.), deep coma, and in most cases a complete absence of sweating, and failure of major organ systems.
At least three factors determine the thermal balance of the body: metabolic heat production, heat exchange between the organism and its surroundings, and heat loss by the evaporation of sweat (Knochel, J. P. [1980] “Clinical Physiology Of Heat Exposure,” In Clinical Disorders Of Fluid And Electrolyte Metabolism, M. H. Maxwell And C. R. Kleeman, Eds., Mcgraw-Hill, New York). For the subject exercising or working, particularly in a hot environment, the capacity to dissipate metabolically produced heat depends for the most part on the subject's ability to form and vaporize sweat (Costill, D. L. And K. E. Sparks “Rapid Fluid Replacement Following Thermal Dehydration,” J. Appl. Physiol. 34(3):299-303, 1973; Greenleaf, J. E. “Hyperthermia And Exercise,” Int. Rev. Physiol. 20:157-208, 1979).
During exercise, especially in a hot environment, serious deficits in effective circulating volume may occur. Muscular work, independent of environment, results in massive shunting of blood to skeletal muscle, along with a substantial loss of plasma volume into the working muscle. Moreover, effective circulating volume is also diminished by losses of sweat (Knochel [1980] supra). The deficit in intravascular volume impedes the delivery of heated blood to the periphery for evaporative cooling. Thus, in the dehydrated exercising subject, there is a progressive increase in the core body temperature as sweat losses accumulate.
Notable among the many physiological responses to physical exertion are increased body temperature, perspiration and pulse rate, a decrease in the blood volume, and biochemical changes associated with the metabolism of compounds to produce energy. In addition, approximately 90% of the body's energy is created by oxygen. All of the activities of the body, from brain function to elimination, are regulated by oxygen. Blood plasma holds approximately three percent (3%) dissolved oxygen, and red blood cells (hemoglobin) hold ninety-seven percent (97%). From the red blood cells the oxygen passes out into the plasma and is transferred to cells that need oxygen during metabolic processes. These cells pass CO2 back to the plasma where it is then picked up by the red blood cells. This process rapidly increases, for example, during exercise and strenuous training.
Prior research in the art has focused on the ability of glycerol to cause water retention. However, water retention alone has little or no correlation with enhanced endurance or physiological performance. In order to have a beneficial effect on endurance and performance, water must be appropriately allocated throughout the body. Mere reduction in urine output is insufficient. Water must be available for sweating (efficient cooling), hydration of cells, and plasma volume must be maintained. Only if these physiological objectives are met can endurance and performance be enhanced.
Osmotic pressure is primarily responsible for the direction and rate of movement of water across semi permeable membranes in the body. Thus, water will move across a semi permeable membrane such that the net flow of water will be across the membrane into the fluid which initially had the highest concentration of solutes, and thus the allocation of water between digestive organs, blood plasma, and cells depends upon the relative osmotic pressures between these sites. Although it has been established that the ingestion of massive amounts of glycerol results in the retention of water within the body (i.e., the rate of urine flow is decreased), this observation alone produces no information as to whether the body's physiological responses to heat or physical exertion have been enhanced. For example, a large concentration of glycerol in the stomach or intestine can cause water to move across the gastrointestinal membranes into the digestive tract and cause detrimental responses to physical exertion and heat exposure. Alternatively, high concentrations of plasma glycerol can cause water to leave the cells and enter the plasma, resulting in detrimental cellular dehydration.
There is, therefore, a pronounced need in the art for novel and effective methods to enhance exercise performance and recovery time and related conditions as described herein.